The present invention relates generally to semiconductor fabrication and, more particularly, to a spin, rinse, and dry station for spin rinsing a bottom side of a semiconductor wafer and a method for spin rinsing a bottom side of a semiconductor wafer.
In the fabrication of semiconductor devices, a variety of wafer preparation operations are performed. In one such preparation operation, deionized (DI) water is sprayed onto the wafer in, e.g., a spin, rinse, and dry (SRD) station, to rinse off the residual chemical solution and to remove particulate contamination. Until recently, efforts to rinse effectively and to control wafer contamination have primarily focused on the top side of wafers. As the semiconductor industry moves to larger, e.g., 300 mm, wafers and to smaller, e.g., 0.18 xcexcm and smaller, feature sizes; however, it is becoming increasingly more important to rinse effectively and to control wafer contamination on the bottom side, i.e., the backside, of wafers. FIG. 1A is a simplified schematic cross-section illustrating one conventional technique used to spray DI water onto the bottom side of a wafer in an SRD station. As shown therein, wafer 10 is supported by rollers 14, which contact the edge of wafer 10 to avoid introducing particulate contaminants to either top side 10a or bottom side 10b of the wafer. A nozzle 16, which is coupled to a source 18 of DI water via liquid supply tube 20, is positioned at the bottom of bowl 12. As wafer 10 is spun, nozzle 16 sprays DI water toward the bottom side 10b of the wafer.
To thoroughly clean the bottom side of a wafer, it is imperative that the spray of DI water contacts the center of the wafer. If the spray contacts only a peripheral portion of the wafer, then the centrifugal force generated by the rotation of the wafer prevents the DI water from reaching the center of the wafer. As a result, residual chemical solution and contaminants, e.g., particles, may not be removed from the central portion of the bottom side of the wafer. If the amount of particulate contamination on the bottom side of the wafer exceeds acceptable levels, then the yield rate may be decreased significantly.
FIG. 1B is an enlarged view of nozzle 16 shown in FIG. 1A. As shown in FIG. 1B, nozzle 16 includes a base portion 16a from which a pair of generally elbow-shaped outlets 16b extend. The upright sections of outlets 16b are angled slightly inwardly, i.e., slightly toward base portion 16a. Below base portion 16a, threaded portion 16c and connector portion 16d are provided. Threaded portion 16c is screwed into a fixture disposed below the bottom of bowl 12 (see FIG. 1A) to hold nozzle 16 in place. One end of liquid supply tube 20 (see FIG. 1A) is coupled to connector portion 16d. 
As shown in FIG. 1A, nozzle 16 is positioned a distance from the center of the bottom of the bowl because a rotatable shaft, which rotates the spindle arm and spindle fingers to which rollers 12 are attached, is positioned at the center of the bottom of the bowl. As a result of this off-center positioning, the DI water sprayed from outlets 16b of nozzle 16 is directed toward the peripheral portion of the bottom side 10b of wafer 10. The elbow-shaped outlets 16b are formed of rigid plastic and therefore the position of such outlets can be adjusted only to a minimal extent, if at all. Furthermore, once nozzle 16 is fully screwed into the fixture, the height of nozzle 16 is fixed and cannot be raised.
In light of the limited adjustability of the nozzle in a conventional SRD station such as shown in FIG. 1A, problems have been experienced in configuring the system so that DI water sprayed from the nozzle contacts the center of the bottom of the wafer. To further complicate the situation, once the wafer is disposed in the bowl, an operator cannot tell where DI water contacts the bottom side of the wafer because the opaque wafer blocks the operator""s line of sight. Thus, even if limited adjustments are made, the operator has no reliable way of determining whether the spray of DI water is properly contacting the center of the bottom side of the wafer.
In view of the foregoing, there is a need for a method and device for spin rinsing a bottom side of a wafer that ensures that the spray of DI water contacts the center of the wafer.
Broadly speaking, the present invention fills this need by providing a nozzle assembly including an adjustable nozzle. By adjusting the position of the adjustable nozzle, the nozzle may be oriented so that liquid sprayed therefrom is directed toward the center of the bottom side of a semiconductor wafer. The present invention also provides a spin, rinse, and dry station including the adjustable nozzle assembly and a method for spin rinsing a bottom side of a semiconductor wafer.
In accordance with one aspect of the present invention, a nozzle assembly is provided. The nozzle assembly includes a connector tube having a first end and a second end. An outer surface of the connector tube is threaded. A first cap having an opening therethrough is threaded onto the first end of the connector tube. A second cap having an opening therethrough is threaded onto the second end of the connector tube. Each of the first and second caps has a top surface and a threaded inner surface. The nozzle assembly further includes a nozzle having a tubular portion defining a channel. The tubular portion is disposed in the opening of the first connector cap so that a position of the nozzle can be axially and rotationally adjusted.
In one embodiment, the nozzle assembly further includes first and second nuts disposed on the connector tube. If desired, one of the first and second nuts may be integral with the connector tube. The threaded inner surfaces of the first and second connector caps preferably have a first diameter and the openings in the top surfaces of the first and second connector caps preferably have a second diameter, with the second diameter being smaller than the first diameter. In this embodiment, tapered surfaces extend between the threaded inner surfaces of the first and second connector caps and the openings in the top surfaces of the first and second connector caps.
In one embodiment, the nozzle further includes a head portion having a channel defined therein. In this embodiment, the channel defined in the head portion of the nozzle is preferably at an angle of about 35 degrees to about 75 degrees relative to a plane perpendicular to the channel defined in the tubular portion of the nozzle.
In one embodiment, first sealing members are provided proximate to the top surfaces of the first and second connector caps, and second sealing members are provided proximate to the first and second ends of the connector tube. In this embodiment, the first sealing members are preferably split ring seals and the second sealing members are preferably bulkhead fitting seals.
In accordance with another aspect of the present invention, a spin, rinse, and dry (SRD) station for spin rinsing a semiconductor wafer is provided. The SRD station includes a bowl having a bottom wall and a sidewall. A rotational member is disposed in the bowl, with the rotational member being attached to a rotatable shaft. A plurality of support members are attached to the rotational member, with the support members being configured to support a semiconductor wafer above the rotational member. The SRD station also includes a motor for rotating the rotatable shaft and an adjustable nozzle assembly mounted in the bowl. The adjustable nozzle assembly is positioned so as to direct a spray of liquid toward a center of a bottom side of a semiconductor wafer supported in the bowl.
The adjustable nozzle assembly preferably further includes a liquid supply tube disposed in the opening of the second connector cap. The liquid supply tube is preferably coupled to a source of deionized water.
In one embodiment, the adjustable nozzle assembly is disposed in an opening in the bottom wall of the bowl. In this embodiment, the adjustable nozzle assembly includes the components specified above, with the tubular portion of the nozzle being disposed in the opening of the first connector cap so that a position of the nozzle can be vertically and rotationally adjusted. In another embodiment, the adjustable nozzle assembly is disposed in an opening in the sidewall of the bowl. In this embodiment, the adjustable nozzle assembly includes the components specified above, with the tubular portion of the nozzle being disposed in the opening of the first connector cap so that a position of the nozzle can be horizontally and rotationally adjusted.
In one embodiment, the adjustable nozzle assembly further includes first and second nuts disposed on the connector tube. The first and second nuts secure the connector tube to either the bottom wall or sidewall of the bowl, depending on how the adjustable nozzle assembly is mounted in the bowl.
In accordance with yet another aspect of the present invention, a method for spin rinsing a bottom side of a semiconductor wafer is provided. In this method a bowl having an adjustable nozzle for spraying liquid toward a bottom side of a semiconductor wafer disposed in the bowl is first provided. Liquid is then sprayed from the adjustable nozzle onto a center of the bottom side of the semiconductor wafer. Preferably, before liquid is sprayed, the adjustable nozzle is oriented such that liquid sprayed therefrom is directed toward the center of the bottom side of the wafer.
In one embodiment of the invention, the operation of orienting the adjustable nozzle includes (a) orienting the adjustable nozzle such that the adjustable nozzle is pointed toward a position where the semiconductor wafer will be disposed in the bowl for spin rinsing, (b) disposing a substantially transparent substrate in the bowl in the position where the semiconductor wafer will be disposed for spin rinsing, (c) spraying liquid from the adjustable nozzle toward a bottom side of the substantially transparent substrate; (d) observing where the liquid contacts the bottom side of the substantially transparent substrate, (e) adjusting the position of the adjustable nozzle in the event the liquid does not contact a center of the substantially transparent substrate, and (f) repeating operations (b) through (e) until the liquid contacts the center of the substantially transparent substrate.
The nozzle assembly of the present invention advantageously enables an operator to adjust easily the position of the nozzle to compensate for tolerances in the spin station, e.g., the spindle height may vary from spin station to spin station. In the method for spin rinsing a bottom side of a semiconductor wafer of the present invention, a substantially transparent substrate is advantageously used to orient the adjustable nozzle to ensure that liquid, e.g., DI water, is sprayed onto the center of the bottom side of a semiconductor wafer. This ensures that the entire bottom side of the wafer is thoroughly rinsed. Testing has confirmed that use of the nozzle assembly of the present invention with the adjustable nozzle properly oriented yields improved wafer particle counts on the bottom side of semiconductor wafers relative to the conventional nozzle shown in FIGS. 1A and 1B.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.